Harmful algal bloom

A harmful algal bloom (HAB) is an algal bloom — a dense aggregation of phytoplankton, algae or cyanobacteria in a marine or aquatic environment — that causes negative impacts to other organisms via production of natural toxins, mechanical damage to other organisms, or by other means. HABs are often associated with large-scale marine mortality events and have been associated with various types of shellfish poisonings.